According to Khobragade's lawyer she had immunity when she was arrested in December for allegedly making false declarations in a visa application for her maid.

Indian diplomat Devyani Khobragade’s status as a “Special Advisor” to the UN entitled her to diplomatic immunity from prosecution at the time of her arrest last year on visa fraud charges, according to a letterfrom the United Nations.
The letter from UN Assistant Secretary General for Legal Affairs Stephen Mathias was submitted in a US court by Khobragade’s lawyer Daniel Arshack to bolster the claim that she had immunity when she was arrested in December for allegedly making false declarations in a visa application for her maid.
Arshack said the 39-year-old diplomat was credentialed as a “Special Advisor” to the UN from August 26 to December 31 last year.

He said Khobragade was appointed an advisor in August last year ahead of Prime Minister Manmohan Singh’s visit for the UN General Assembly session.
Given that Khobragade had a UN credential of Special Advisor, she was immune from arrest on December 12 and prosecution on visa fraud charges, he said.

Arshack submitted the letter from the UN Assistant Secretary General as an exhibit in court along with his motion to dismiss the indictment against Khobragade.
The letter states that according to the Convention on the Privileges and Immunities of the UN adopted by the General Assembly, “…representatives of members to the principal and subsidiary organs of the United Nations and to conferences
convened by the United Nations shall, while exercising their functions and during their journey to and from the place of meeting, enjoy the…privileges and immunities” set forth under sections of the Convention unless the person is a “representative in a state of which s/he is a national or of which s/he has been a representative”. It said the expression representatives “shall be deemed to include all delegates, deputy delegates, advisers, technical experts and secretaries of delegations”.

The letter clarified that application of the rules of immunities in any specific situation “would depend on the facts and circumstances of the specific situation”.

Khobragade was strip-searched and held with criminals after her arrest, triggering a diplomatic row between India and the US. After her indictment on visa fraud, she returned to India in January after she was asked to leave the US by the State Department.